technique for repairing broken plastic clips

[bigmessowires]

Can broken plastic clips from Macintosh cases be effectively repaired? If so, what type of adhesive do you use to reattach the broken piece? These are parts that are meant to bend a little, like the clips that hold on a case lid, or that secure the fan, drives, and logic board in place for some models. I have a lot of broken clips recently from over-aggressive bending. The adhesive would need to be something that can handle a bit of lateral force when the clip is bent.

 

[Byrd]

Having come across many a broken clip on Mac cases, a quick rundown of my efforts:

- CA glue - no good on small clips but good for large long chunks (eg. broken bezels with long seam can be repaired without much visible damage). CA glue + baking soda allows you to strengthen the bond but can get messy and is only good for clips you don't see.

- JB Weld - good in some instances, again for clips you don't see owing to colour, use to stabilise areas around clips. JB Weld + 3D printed brackets are next level, eg PowerBook lugs and hinges

- ABS cement - yet to dry, have heard that shavings of same plastic + put overnight in small jar of acetone to make a glue is very effective

- Good quality epoxy such as the stuff that dries clear (Gorilla brand) - has some flex, good for large clips with glue stabilising the side you can't see

Another thing to try is before you glue the clip back on, to shave down the clip a mm or two so it doesn't need to flex as much when removing the part - using a razor or scalpel. This works great for repaired clips such as the ones that breaks on 6100 cases etc.

 

[Phipli]

Acetone works well as a solvent glue but takes a while to set. MEK sets faster, but my my, do not spill these two chemicals on the case - remember the bit in Alien where they cut the facehugger and it bleeds acid?

Brush a small amount into one half of the mating faces and then push them together. The solvent melts the ABS on both sides of the joint, and when it evaporates, you're left with solid plastic.

The main difficulty is keeping it in the right place while it sets.

 

[nightingale]

I have nothing of value to add, other than I feel your pain. I was excited to retrobrite my LC580, then was defeated when all the clips basically turned to crumbs taking it apart. My solution has just been to put it back together as best I can and just never take it apart again. Enough clips survived to hold it together, but it will never have a major move.

 

[LaPorta]

Here’s a related question for a secret project of mine: what would one recommend to adhere steel to said plastic?

 

[Phipli]

Here’s a related question for a secret project of mine: what would one recommend to adhere steel to said plastic?

Roughen the surface first and perhaps use an epoxy. Avoid peeling forces.

 

[rplacd]

That's the nub... how do we find a metal-to-plastic adhesive that's shear resistant? For example, metal screw receptacles in in old PowerBooks break free from the weakened plastic they're embedded in. How do we reconstruct this bond in a way that actualy resists forces twisting/perpendicular to the surface, like twisting a screw?

 

[Phipli]

how do we find a metal-to-plastic adhesive that's shear resistant?

No such thing - glues work well with large surface areas, but are generally susceptible to peel, unless they are plastic solvent types (which don't work with dissimilar materials like this) which reform the material into one, more like a weld.

You use mechanical fastenings around the edge of the glued area to prevent peel. That's what you do in aircraft.

@GRudolf94 might have some input.

 

[Phipli]

PowerBooks break free from the weakened plastic they're embedded in. How do we reconstruct this bond in a way that actualy resists forces twisting/perpendicular to the surface, like twisting a screw?

Oh, this is a different question.

You grind it off, and solvent or heat weld a new ABS tube in place with a centre bore slightly smaller than a threaded insert, then push the threaded insert in using a soldering iron so that the plastic flows around the knurling.

I'd them scuff the area and reinforce it with epoxy. But I'm pessimistic.

 

[GRudolf94]

As far as my knowledge extends, securely bonding metal to plastic usually requires some sort of thermoset resin, or positive mechanical attachment (for instance, heatstakes). Else you'll always end up with the metal peeling off as @Phipli mentioned.

3M 08115 and 08116 might be fun

 

[Phipli]

As far as my knowledge extends, securely bonding metal to plastic usually requires some sort of thermoset resin, or positive mechanical attachment (for instance, heatstakes). Else you'll always end up with the metal peeling off as @Phipli mentioned.

3M 08115 and 08116 might be fun

And prep.

Prep is important with glues, like with paint.

 

[3lectr1cPPC]

Here’s a related question for a secret project of mine: what would one recommend to adhere steel to said plastic?

You're trying to steel-reinforce PowerBook 1400 display housings aren't you!

 

[rplacd]

You're trying to steel-reinforce PowerBook 1400 display housings aren't you!

Woah, woah, don't steal the thunder of the PowerBooks 1xx!

 

[LaPorta]

You're trying to steel-reinforce PowerBook 1400 display housings aren't you!

Darn it all, I forgot you of all people was on this thread!

 

[3lectr1cPPC]

Red handed

 

[zigzagjoe]

A related tidbit for repair of stripped out screw bosses for self-tapping screws. For example, the SE/30 upper screws.

1. Clean the screws
2. Make ABS slurry: acetone and abs mixed until liquid
   1. This must be as thick as possible as that means more plastic content.
   2. Make very certain you are using pure ABS.
   3. 3D printer filament is ideal, or you can experimentally try scrap plastic to verify it fully dissolves.
3. Put ABS slurry into the boss with a toothpick or similar
4. Screw (don't push) the screw into the boss
   1. You should have enough ABS slurry in there that when the screw is fully in, some of the ABS slurry comes out.
5. Wait a day or so
6. Very gently unscrew the screw(s)
7. Wait another day.

This has worked well for my SE/30 that had both stripped. You're effectively putting new plastic in, merging it (not gluing or bonding) to the original ABS while forming threads at that same time. Since the acetone component evaporates, it's going to be weaker than pure ABS would be, but it's been plenty strong for this use and has stood up so far.

 

[Juror22]

I posted this in the lounge back in May (What did you do to your Mac today?)... the piece is still fine and although I haven't been removing that piece, I have taken the case off and put it back on several times since then and it is still holding without change. I think this fix depends on how good the original tab is. In this case (and on the IIvx) they were broken in about this spot which leave quite a bit to work with and adhere to, but maybe this gives you an idea on how to solve your problem.

"The from[front] panel that I sourced had a broken tab, as many of them do, so I had to fix it. I got the idea for the fix from one of the ways of repairing the Powerbook hinges that uses a 3D-printed plastic piece, glued onto the panel. Using a similar idea, I fashioned a plastic end piece for the tab with two pieces that would be glued onto the tab itself and use plastic epoxy within the piece for additional structural integrity.

It resulted in a fix that is solid, has some flexibility (like the original) but will not yield and maintains the correct lines from the outside. It had to look and function correctly and it does line up exactly the same as the original filler panel, which has a perfect tab. I will do a better job of documenting the next one (I have an original IIvx CD panel that needs the same fix and I think this will work for that just as well)."